Multi-level geophone installation for VSP

ABSTRACT

What is disclosed is an improvement in a multi-level geophone sonde installation for VSP which includes a well penetrating subterranean formations; surface source for generating and inputting vibrational wave energy; a plurality of geophone sondes with a plurality of detachable geophone sondes disposed in the well with an uppermost sonde and at least a plurality of other lower sondes at predetermined spacings for receiving vibrational wave energy arrival and generating the data indicative thereof; and conductors for getting to the earth&#39;s surface a record of the vibrational wave energy arrival data. The cable has a greater width than thickness and is rigid because it is formed in a plurality of vertebrae type formations so that it is self supporting or load bearing. Moreover, the rectangular cable reduces the twist of the cable. The cable has at least two longitudinal load-bearing cables for bearing the entire load of the plurality of geophone sondes and a plurality of longitudinal conductors operationally connectable to the geophone sondes so as to carry to the earth&#39;s surface signals indicative of the vibrational wave energy arrival data; and a holder for holding the cable at least adjacent the upper sonde and adapted for holding the entire weight of all the sondes.

FIELD OF THE INVENTION

This invention relates to vertical seismic profiling. More particularly,this invention relates to an improvement in a multi-level geophoneinstallation for vertical seismic profiling (VSP).

BACKGROUND OF THE INVENTION

The prior art literature is replete with a wide variety of verticalseismic profiling information. An excellent bibliography is contained atthe back of the book entitled "Vertical Seismic Profiling"; part Aprinciples; Bob A. Hardage; HANDBOOK OF GEOPHYSICAL EXPLORATION, SectionI Seismic Exploration; Claus Helbig and Sven Treitel (Editors);Geophysical Press Limited, Westcombe House, 56-58 Whitcomb Street,(multiple volumes) London WC2H7DR, United Kingdom, 1983. As noted inthat book, the Russians have used vertical seismic profiling technologyfor at least the past twenty-five years and it has become increasinglyimportant in exploration techniques in the free world, particularly, inthe United States. That bibliography, or references beginning at page421, contains records of a wide variety of different approaches,including theoretical treatises and practical installations. As noted inthe preface to that book, the inventor of this invention is given creditfor significant contributions in the western world, or free world.

The closest prior art of which I am aware is a cable developed by theKerite Company. Various production committees have suggested that cablewould be useful for lowering into the well downhole pumps or the like.This would obviate the requirement for separate load-bearing linealmeans, such as tubing, to support the pump and facilitate installationand even removal for repair of downhole pumps or the like.

One of the problems that has been concomitant with vertical seismicprofiling in the past has been the unduly long time required to put inmulti-level geophone tool into a well. This is particularly importantwhere an offshore rig is standing by while the vertical seismicprofiling is being performed at a well location. There has been alongstanding need that the prior art has not yet satisfied for amulti-level geophone sonde installation in which the tool could beemplaced and the vertical seismic profile run within a time period ofonly five to six hours, instead of having to have at least a full day ofrig down time waiting for a vertical seismic profile log to be run.

SUMMARY OF THE INVENTION

Accordingly, it is an object of this invention to obviate thedeficiencies of the prior art and provide an improved geophone sondeinstallation where the geophone sondes can be arranged at a plurality ofdepths in the well for running a vertical seismic profile log in only atime period of five to six hours so as to obviate the requirement ofhaving downtime of at least a full day or more.

It is a specific object of this invention to provide an improvedmulti-depth geophone sonde installation in which a single cable providesthe load-bearing capability as well as the bringing to the surfacesignals representative of the wave energy arrival data to the respectivegeophone sondes at a plurality of depths in the well and withoutrequiring separate running of the load-bearing lineal means with thecapability of bearing the load of the plurality of geophone sondes andeliminating the necessity of separate conductor means for the respectivegeophone sondes run independently of the load-bearing lineal member,especially including means for making electrical interconnectionsbetween the respective geophone sondes and the conductors in theload-bearing cable.

These and other objects will become apparent from the descriptive matterhereinafter, particularly when taken into conjunction with the appendeddrawings.

In accordance with this invention, there is provided an improvement in amulti-level geophone sonde installation which in the prior art hasincluded a well penetrating from the earth's surface into thesubterranean formation, a surface source for generating an inputvibrational wave energy at the earth's surface, a plurality of geophonesondes with a plurality of geophones disposed in the well adjacent theborehole wall thereof and held against the borehole wall, with anuppermost sonde in a predetermined spacing therebelow, lower sondesbeing provided for receiving the vibrational wave arrival energy by wayof the earth; and means for getting to the earth's surface a record ofthe vibrational wave energy arrival data. The improvement ischaracterized by an untwisted cable that has a greater width thanthickness so as to have a preferred orientation and having load-bearingcables running longitudinally with conductor cables for connecting tothe plurality of geophone sondes and the means for transmitting, orgetting to the earth's surface a record of the vibrational wave energyarrival data; and a holder for holding the cable at least adjacent theupper sonde, the holder being adapted to support the weight of thesondes and associated equipment below the uppermost sonde and allowslacking off of the cable from the uppermost sonde to the surface of theearth so as to minimize downgoing signals from the surface source.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a prior art installation, such asdisclosed in the hereinbefore referenced text "Vertical SeismicProfiling".

FIG. 2 is a partial schematic illustration of a well bore with amulti-level VSP geophone system installed in the well bore penetratingsubterranean formations.

FIG. 3 is a somewhat schematic illustration of a cable spool employed asthe means for unspooling into a well bore penetrating the subterraneanformation a cable in accordance with the one embodiment of thisinvention.

FIG. 4 is a schematic illustration one embodiment with a plurality ofconductors in the center between two load-bearing cables in the cablemeans.

FIG. 5 is another view showing greater detail of the cable in accordancewith an embodiment of this invention.

FIG. 6 is a cross-sectional view of the cable of FIG. 5.

FIG. 7a is a partial isometric view of a plurality of geophone sondesand a load-bearing cable and signal carrier in accordance with anembodiment of this invention.

FIG. 7b is a schematic cross-sectional view showing the geophone sondedisposed in a well with standoff nodes and arms.

FIG. 8a is a schematic illustration of one embodiment of this inventionin which a holder is employed adjacent the top geophone sonde forallowing slacking off of the cable thereabove to minimize downgoingsignals.

FIG. 8b is a schematic illustration of another holder means inaccordance with another embodiment of this invention for allowingslacking off of the cable thereabove.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIG. 1, an exploring unit 11 is suspended in a well 13penetrating the earth's subterranean formations 15. The exploring unit11 also includes a surface source 17 for generating an input vibrationalwave energy at the earth's surface. The exploring unit 11 also includesa plurality of geophone sondes 19. Disposed in the well adjacent theborehole wall thereof and held against the borehole thereof with anuppermost sonde at a predetermined spacing therebelow, lower sondes forreceiving vibrational wave arrival data; and means for getting to theearth's surface a record of the vibrational energy arrival data,including a surface recording truck 21. The invention is characterizedby an improvement comprising untwisted cable means 25, FIG. 3, having agreater width than thickness, similarly as illustrated in FIG. 4, so asto have a preferred orientation. The cable has at least two load-bearingcables 27, 29 adjacent each edge and adapted for bearing the entire loadof the plurality of geophones and the plurality of conductors 31 betweenthe load-bearing cables lateral of the cable means. The plurality ofconductors are connected so as to carry to the surface signalsindicative of the vibrational energy arrival data. The cable has aplurality of electrical outlet connections for connecting to therespective geophone sondes.

The exploring unit 11 also has a holder means for holding the cable atleast adjacent the upper sonde so that the cable can be slacked off. Theholding means is adapted for holding the entire weight of all geophonessondes and allowing slacking off of the tension of the cable between theupper sonde and the earth's surface so as to minimize downgoing signalsfrom the surface source.

The typical exploring unit of FIG. 1 is well recognized in the art anddoes not need a great deal of application herein. Sufficient to notethat the well 13 is drilled into subterranean formation 15 byconventional techniques. A surface source 17 may comprise explosive orsimply another unit to input vibrational energy. Typical of these inputunits are the air sources, or the weight dropping sources.

The geophone sondes are substantially the same as the geophones that arenormally employed for seismic exploration and detect vibrational energy,except sondes can be, with this invention, smaller and much lighterweight than the prior art, since the cable can be pushed through anyheavy drilling mud. The smaller, lighter sondes are preferred, sincethey will have a high resonance capability by being smaller. The cableis load bearing. Geophones can use the cable as part of theirstabilities in clamping. In prior multi-level sondes, the geophone wasload bearing and had to be much larger and heavier. It is noteworthythat the energy wave arrival data may be sent to the surface as itoccurs or stored and then sent to the surface in a time sharing mode,depending upon the number of conductor channels available in the cableand the number of geophone sondes that are employed downhole.Frequently, the pulse power applied from the source repeatedly energizesthe respective receivers to produce sharp, time-spaced acoustic pulsesor similar pulses indicative of the arrival of the wave energy from thesource 17.

Referring to FIG. 2, an uppermost geophone sonde 19 may be employed witha plurality of downwardly spaced other geophone sondes 19 and connectedby cable 25. The cable 25 intermediate the geophone sondes 19 does nothave to be slacked off but it is advisable to slack off the cable 25above the top geophone sonde in order to minimize interference withdowngoing waves from the wave energy.

Referring to FIG. 3, the cable 25 may be spooled from a holder, or spool33 and input through a unit 35 with a preferred orientation.Specifically, referring to FIG. 4, the preferred orientation will be,ordinarily, with the flat surface input through the unit 35.

The cable 25 is illustrated more nearly completely in FIGS. 5 and 6.Therein the cable 25 includes the respective longitudinally extendingload-bearing cables 27, 29 adjacent each edge with the respectiveconductors 31 intermediate the load-bearing cables. Other arrangementscan be employed as desired.

In the embodiment illustrated in FIG. 7a, the cable 25 has respectivevertebrae 37 and out of each vertebrae is a pressure compensatedconnector 39 that can be connected into a mating connector 41 on top ofeach geophone sonde 19. The illustrated embodiment could be expandedconsiderably. For example, an embodiment could be provided to includethe cables inside load bearing coil tubing. If desired, electrical takeout can be improved and particularly the take out could be added only atvertebrae between adjacent cable sections to maintain cable strength.The drawing of FIG. 7a is not to scale and the vertebrae may be locatedwith the respective electrical connectors, at distances as desired; forexample, five to ten meters. This allows the geophone sondes to beemplaced every five to ten meters in the well.

As illustrated, there are standoff nodules 43, seen in both FIGS. 7a andFIG. 7b that help the respective geophone sondes to be maintained at thedesired position by clamp-off arm 45. The stand off nodules 43 can beused to help attach geophone sondes to the cable during makeup.Specifically, as shown in FIG. 7a, the nodule, or sonde, can be detachedwhen the cable 25 is spooled onto a wire-line drum and attached asneeded. Specifically, the pressure compensated connector 39 can beconnected onto the mating connector 41 at the top of each Geophone sonde19 as illustrated.

Referring to FIG. 8a, the exploring unit 11 with its cable 25 includes aholder 47 at the top adjacent the geophone sonde 19 so as to bear theweight of all lower geophones, as well as the top geophone sonde 19, andassociated downwell equipment. This allows slacking off of the cable 25above the top geophone sonde 19 and alleviate problems with downgoingwave energy traveling by way of a cable under tension.

The holder 47 can take any of the form desired. For example, shown inFIG. 8b, it may simply be asymmetric rollers such as 47b, 47c, 47d, and47e. These asymmetric rollers can be activated as desired to hold thecable 25 and allow slacking off above the rollers, yet hold the cable 25to bear the weight of geophones therebelow.

Expressed otherwise, the holder 47 may comprise a clamping means forclamping the cable with a predetermined orientation, where it is simplyclamped into the wall of the wellbore, as with a clamp arm or the like,or it may comprise any other suitable means such as asymmetric rollersthat hold the cable with a predetermined orientation such as with theflat side gripped by the rollers. The cable does not necessarilymaintain orientation. It will orient itself as it

naturally would be incIined to do. Over 1000 feet or so, where themeasurement will be taken, it may be rigid whereas the prior art wouldbe rigid only for a smaller interval. The orientation may bedeterminable but it should ordinarily, particularly when used in ahorizontal borehole, seek the orientation for the top of the geophonesonde with its arm 45 should seek the top of the borehole if a topexists.

It may be necessary to determine orientations by other sensors of whicha gyro is an example.

From the foregoing it can be seen that this invention accomplishes theobjects set out hereinbefore. Specifically, this invention provides animproved geophone sonde installation wherein the geophones are arrangedat a plurality of depths in a well for running a vertical seismicprofile log in only a time period of five to six hours so as to obviatethe requirement of having a rig downtime of at least a full day or more.

It is worth noting that the geophone sondes have the ability to be usedin high deviation holes such as horizontal or holes that are drilled toapproach horizontal orientation. Moreover, because of the structuralstrength, the cable enables pushing the light-weight, small sondesdownwardly through even bridges that might be lightly formed in a well.It is particularly worth noting that the light weight, small sondes canbe pushed through heavy drilling mud in highly deviated holes or thelike.

Having thus described the invention, it will be understood that suchdescription has been given by way of illustration and example and not byway of limitation, reference for the latter purpose being had to theappended claims.

What is claimed is:
 1. In a multi-level geophone sonde installationwhich includes:a. a well penetrating from the earth's surface deeplyinto subterranean formations; b. a surface source for generating andinputting vibrational wave energy at the earth's surface; c. a pluralityof geophone sondes with a plurality of geophone disposed in said welladjacent the bore hole wall thereof and held against the borehole wallthereof with an uppermost sonde and a predetermined spacings therebelow,lower sondes for receiving vibrational wave energy arrival data; d.means for getting to the earth's surface a record of said vibrationalwave energy arrival data;the improvement comprising: e. an untwistedcable means having a greater width than thickness so as to have apreferred orientation; said cable having a least two load-bearing cablesadjacent each edge and adapted for bearing the entire load of saidplurality of geophones and a plurality of conductors between saidload-bearing cables laterally of said cable means; said plurality ofconductors being connected so as to carry to the surface signalsindicative of said vibrational energy arrival data; said cable having aplurality of electrical outlet connections for connecting theretorespective said geophone sondes; and f. holder means for holding saidcable at least adjacent said upper sonde; said holding means beingadapted for holding the entire weight of all sondes and allowingslacking off of tension on said cable between said upper sonde and saidearth's surface so as to minimize downgoing signals from the surfacesource.
 2. The improved system of claim 1 wherein said holder meansincludes a clamping means for clamping said cable means to a geophonesonde with a determined orientation.
 3. The improved system of claim 1wherein said cable means is in the form of a plurality of vertebrae witha continuous set of load-bearing cables at each side with a plurality ofelectrical outlet connections at respective plurality of predeterminedspacings along said cable beginning at a predetermined depth distancealong said cable when said cable is lowered into said well.
 4. Theimproved system of claim 3 wherein said plurality of vertebraecomprising said cable means impart the ability to deploy a geophonesystem in heavy drilling mud, deviated wellbores and even horizontalwells.
 5. A system for use in seismic surveying in a borehole,comprising:a. a cable assembly having at least two load bearing cablesseparated from each other and electrical conductors interposed betweensaid load bearing cables; b. said cable assembly having pluralelectrical takeoff connectors coupled thereto, said connectors beingspaced along a length of said cable assembly in predetermined intervals;c. plural geophones removably coupled to said cable assembly and coupledto selected ones of said connectors.
 6. The system of claim 5 furthercomprising means for slacking off of that portion of said cable assemblythat is above an uppermost geophone on said cable assembly, saidslacking means being coupled to said cable assembly.